field



4 Sheets-Sheet 2.

(No Model.)

D. FIELD.

ELEQTRIC LQCOMOTUR.

Patented Apr. 10

, Vida/4A) N. PETERS Pmm-Lima m hor, Washington, 11 C.

(No Model.) 4 Sheets-Sheet 4.

y S. D. FIELD.

ELBGTRIG LOGOMOTOR. v No. 380,879. Patented Apr. 10, 1888.

N Pains, Phnlb-Lilhagmphur. Washington. we.

. well as the direction of its movement.

, NITED STATES ATENT rrrca.

STEPHEN DUDLEY FIELD, OF YONKERS, NE\V YORK.

ELECT RlC LOCOMOTOR.

SPECIPICATIQN forming part of Letters Patent No. 380,879, dated April10, 18188.

Application filed December 9, 1886. Serial No. 22l,064.

To all whom it may concern:

Beit known that I, STEPHEN DUDLEY FIELD, a citizen of the United States,residing in Yonkers, in the county of \Vestchester and State of NewYork, have invented certain new and useful Improvements in ElectricLocomotors, of which the following is a specification.

The invention relates to the propulsion of vehicles by means ofelectricity. It comprises certain improvements in the construction ofelectric motors, the adaptation of the same to moving vehicles, themethod of mounting the same upon the vehicles, the manner of connectingthe armature with the drivingwheels of the vehicles, the devices forsupplying currents thereto, and the devices for regulating andcontrolling the current supplied to the motor. t

The general construction of the electric locomotive may be brieflydescribed as follows: The field'magnet of a suitable electric motor issupported through yielding springs from the axles of the wheels of atruck, and'the armature is coupled with the wheels by rigidconnecting-rods attached to suitable crankpins. The rotary motion of thearmature is communicated through these connecting-rods to the wheels ofthe truck. The body of the car or vehicle is supported upon the truck bymeans of a turn-table resting upon the fieldmagnet and a frame supportedupon suitable springs from the field magnets and axles. The currents aresupplied to themotor from a stationary generator, either through one ofthe ordinary rails of the track or from an independent parallel rail orconductor especially provided for that purpose. The connections betweenthe vehicle and the rail or other supplyconductor are made through acontact wheel or roller revolving in a plane oblique to the direction ofmotion of the vehicle for the purpose of securing a reliable electricalconnection, as hereinafter shown. The electric currents are led fromthis contact wheel through the necessary adjustable resistances andcircuit-controlling devices to the motor proper. The resistances andcircuit-controlling devices referred to serve to modify the speedrotation of the armature of the motor as A supplementary electric motoris employed, when required, for actuating the circuit-controlling (Nomodel.)

devices. position of the commutator and the brushes with reference toeach other both for the purpose of varying the speed of the motor andreversing its direction. It also performs the office of maintaining thecommutator-brushes in such position with reference to the neutral lineof the commutator as to cause the current to be supplied with a triflingloss of energy and entire freedom from sparking and burning. The circuitand current controlling devices and the switchlocking mechanism are not,however, fully claimed herein, as it is proposed to make them thesubject-matter of another application for Letters Patent.

The invention also comprises many details of construction andorganization, whichwill be hereinafter described in connection with theaccompanying drawings, forming part of this specification.

Referring to the drawings, Figure 1 is a plan'of the motor as applied tothe wheels of a railway-truck; and Fig. 2 is a side elevation of thesame, partly in section. Fig. 3 is an end view of the motor, also partlyin section. Fig. 4 is a detail view of the commutator and itscontrolling devices, and Fig. 5 is a section of the same. Fig. (Sshowsin diagram the cir- It serves to automatically adjust the acuit-connections of the apparatus, and Fig. 7

is a detail drawing of the current reversing and controlling device.Fig. 8 is a detail of the armature. Fig. 9 illustrates a modification inthe organization of the circuits and controlling apparatus.

Referring to the figures, A Alrepresent the two axles of the truck of arailway-motor. These axles are provided with wheels 0 a and a a,respectively. The field-magnet of the motor is mounted upon the axles AA by means of yielding springs, as represented at B The field-magnethere shown consists of two cores, 'B B put together so as to formconsequent poles, and respectively extending above and below thearmature C. The axlesprings 13 are preferably inserted in boxes B at theends of the field-magnet cores and rest upon brasses B which are fittedto receive the journals of the axles. A sliding linchblock, B, holds theparts in position with reference to each other. Sufficient room is al-'lowed in the boxes 13* for the brasses B to slide up and down andprevent sudden shocks upon the motor from the movements of the axles.

For the purpose of obviating the production in the armature of Foucaultor other extraneous currents it is preferred to construct the same of aconsiderable number of soft-iron rings or annular disks separated fromeach other by thin sheets of paper and glue. These rings or disks areheld together by the wire enveloping the armature, no bolts or otherconducting materials being employed for the purpose.v In an armatureconstructed in this manner the unequal expansion of the copper and ironunder the influence of the heat developed in the armature when runningtends to loosen the separate parts of the same. To avoid this,sheets ordisks ofsome other metal-- such, for instance, as zincare interspersedwith the iron disks. These are arranged in such proportion and order asto give to the entire armature-core a total coefficient of expansionequal to that ofthe copper wire. The armature is wound in any well-knownor desired manner, and is adapted to revolve within a chamber formedbetween the poles of the field-magnet, the electrical connection andrelation between the field-magnet and the arma ture being preferably ofthe same character as in the case of a dynamo-electric generator-- thatis to say, they are connected either in series with each other or theone in a shunt upon the other, as required under different conditions.The coils O of the armature are preferably wound through the interior ofthe hollow iron core and over its external surface from end to end. Theshaft 0 of the armature extends within the opening through the disks andis firmly secured in a central position. It is preferred to surround theshaft by a brass collet, 0 upon which there is placed a wooden sleeve orcylinder, 0*. This is secured by disks (3 at the ends of the collet.Four plates of wood, C 0, having their outer surfaces curved to theinner surface of the armature-coils,are placed within the armature nextthe wire. These widen toward the center and are bound in position bywedges C 0, bearing against the sleeve 0. The brass collet is keyed tothe shaft by wedgeshaped keys G which are of advantage in centering thearmature.

The field-magnet is constructed with aspider having arms b, b b and b"at one end converging to form a bearing, 0', for that end of thearmature-shaft. The other end of the fieldmagnet is provided withasimilar spider, forming a bearing, 0 for the other end of thearmature-shaft. These spiders are preferably bolted to the ends'of thefield-magnets in the manner shown, as this forms a convenient mechanicalconstruction and one which gives 'a solid support for the revolvingarmature.

The journals or bearings are designed to be fitted in any well-knownmanner for convenience of lubrication and for compensating for the wear.

Upon the respective ends of the armatureshaft 0 are fixed cranks D and DThese are designed to take hold of connecting-rods d d and cl 01*,respectively. The connectingrods (1 and d couple the crank D with thetwo wheels a and a by means of crank-pins c and a which may be insertedinto the sides of the wheels at suitable distances from their centers.In like manner the rods d and d connect the crank D with the pins e e ofthe wheels at and a. The cranks D and D are preferably placed at anangle of ninety degrees to each other, so that there may be nodead-point in the armature with reference to the wheels and that therotary motion of the armature may be transmitted to the wheels by forcesparallel to a line connecting the centers of the driver-wheels.

The crank-arms D and D" extend into suitable sliding boxes, d fittedinto the connecting-rods at the point between the corresponding pins.These permit the necessary play of the crank during the revolution ofthe armature, and at the same timepermit the parts to adjust themselvesfor any relative movement between the motor and the axles due to theaction of the springs B.

The body of the vehicle is preferably supported upon a turn-plate orfifth-wheel, F, which is stepped in a bar, F, at the top of thefield-magnet at or near its center. The body itself bears upon a frame,E, which is supported above the axles by means of yielding springs f, f,and f, of any suitable character. These springs rest directly upon theboxes B of the respective axles and serve to ease the rocking movementsof the Vehicle with reference to the truck. The frame F is provided withcurved slots f and f for receiving corresponding projections from thebody of the vehicle. These bind it thereto, while permitting asufficient swiveling movement of the truck upon its turn-plate F inpassing a curve.

It will be understood that any of the usual forms of spring-buffers maybe employed for preventing jolts and irregular movements of the truckfrom being communicated to the body of the vehicle.

The electric currents are preferably conveyed to the motor through aninsulated contact-rail, G. This niay,with advantage, consist of anordinary track-rail laid along the bed of the road, preferably betweenand parallel to the two ordinary rails, G and G", but at a littledistance from one of them. This conductingrail may with advantage besupported upon a plate of insulating material, g, which rests upon aplank, g, laid upon the road-bed, which serves to raise it above thelevel of the other two rails. In this case the contact devices forcollecting the current therefrom are not required to extend downward aslow as the supporting-wheels of the truck.

Theparticular form ofcontact device which it is preferred to employconsists of a brushwheel, H, made up of thin plates of brass, steel, orother suitable material (shown at h h) placed side by side and boundtogether to form a wheel of sufficient breadth. The edges of these disksor plates possess sufficient resilience to insure the making of a goodelectrical contact and to give a certain flexibility to the periphery ofthe wheel. The contact-wheel is carried in a bearing or yoke, H, and isset in a vertical plane oblique to the direction of the rail G, so thatthe movement ofthe motor will cause it-torevolve on its axis, and at thesame time to rub angularly upon the surface of the rail.

For the purpose of easily adjusting the p0- sition of the brush-wheel Hthe yoke H is carried by an arm, h, mounted in suitable bearings, h" hwhich permit it to be turned horizontally in one direction or the otherfor adjustment. An arm, h, extends from the end of the support h and isprovided with a setnut, h and bolt h, extending througha quadrant, if.The curve of the quadrant permits the rod h to turn, and by means of theset bolt and nut it may be securely fastened in any desired position. Aspring, h exerts a force tending to press the rod, and consequently thebrush-wheel h, downward against the surface of the rail G to secure anefficient and at the same time an adjustable contact. The nuth", againstwhich this spring presses, is preferably adjustable, and it serves bystriking against the bearing If to determine how far the wheeland itssupport shall be pressed downward. The connections from thecontact-wheel H are through a conductor, 1, to an adjustable artificialresistance, B. This resistance is constructed in sections 1" r 1", &c.,with connecting plates 8 s" 8 820. A contact-brush, It, is movable alongthe plates for the purpose of including more or less of the sections 1"1- r, &c., in circuit. The last plate, s of the series is not connectedwith the resistance, and hence when the brush R rests upon it thecircuit is interrupted. The brush R is carried upon a nut, J, movablealong a screw-threaded rod, J. This rod, when turned in one direction,carries the nut, and thus the brush R, to one end otthe resistance R.\Vhen rotated in the opposite direction, it moves the brush It towardthe opposite end of the resistance R.

For the purpose of conveniently turning the rod J as desired itisconnected by bevel-gear t" t with a rod, i, which is provided with ahandwheel, 1;, of any suitable character. By turning this wheel in onedirection or the other the position of the brush B may be varied and thecurrent which will be delivered through the brush correspondinglyregulated,according to the amount of resistance interposed in thecircuit. From the contactbrush R the current traverses a conductor, 2,to one plate, K, ofa

' circuitcontrolling device, K. A second plate,

K of the same device is connected by a con ductor, 3, with one terminalof the field-magnet coils of the motor. A conductor, 4, connects theother terminal of the fieldmagnet coils with a contact-brush, N, bearingagainst one of the axles of the truck, which thus completes the circuitwith the rails G and G of the main track.

The circuit-changer proper, K, is applied to four contact-points, is,If, k and 7c. These combined with the circuitchanger K form acircuit-controller for the armature of the motor. The plates 7t and kare united by a conductor, 5, and also by a conductor, 6, with the brushN of the armature. The contact-plates k and are united by a conductor,7, and by a conductor, 8, are connected with the terminal brush N of thearmature. The plate K may be shifted so as to bring it in contact eitherwith the plates is and k or with the plates Zr and k as desired. \Vhenin the position shown in the drawings, the current passes in onedirection through the armature-coils and a shunt from this circuitincludes the fieldmagnet coil. \Vhen the position of the plate K isreversed, the direction of the current through the motor'armature willalso be reversed, although the direction through the field-magnet coilswill remain unchanged.

For the purpose of conveniently controlling the position of thereversing plate K a rod, 0, couples the plate with a hand-lever, O.

As it is undesirable for many reasons to re verse the connections whenthe motor is under the influence of a strong current, it is preferredthat the lever 0 should be movable only when either a very large amountof the resistance R is in circuit or else when the circuitis completelyinterrupted by the contact of the brush R with the plate 8 The lever Ois therefore placed in such position with reference to the brake-wheelt" that an arm, 0, is locked by a flange, 0", on picking-up wheel,except when the brush It is in a predetermined position. The flange 0 iscarried upon a wheel, 0", gearing with a pinion, 0", upon the rod Theflange 0 has an opening, 0, through which an arm, 0', upon the lever 0may pass freely when the wheel is in its predetermined position forunlocking.

It remains now to'describe the connections between the brushes Nand Nand the commutator P. This commutator is constructed with a series ofcontact sections or segments with which the brushes N and N makecontact. The commutator is secured rigidly to the armatureshaft andrevolves therewith. The brushes N and N however, are mounted upon aring, 5, supported upon suitable trio tion rollers, S, which permits itto be revolved upon its axis. The brushes N and N are affixed tosuitable supports, T and T, which permit them to be inclined in onedirection or the other with reference to the neutral axis of thecommutator, according to the direction of tending through slots t.Springs a serve to press the brushes toward the commutator. Aprojection, n upon each brush is employed for limiting the movement ofwhich each brush is capable upon its axis a by contact with twoadjustable screws or stops, it and 6, carried in the support T.

It is well known that'at a certain position of the commutator withreference to the armature, known as the neutral axis, there will be lesssparking than at any other point, and it is usually desirable tomaintain the contact of the brushes at such points. For this reason ithas been customary usually to adjust the brushes by hand. It may be doneautomatically, however, in the following manner: A subsidiary motor, U,acts to adjust the position of the ring S, and thus of the brushes N andN To this end the field-magnet u of the motor U is included in ashunt-circuit from the brushes l and N by conductors 10 and 11,extending from the conductors 8 and 6. The armature of this motor,however, is included in a separate circuit derived from contact brushesV and VZapplied to the commutator. These brushes are constructed much inthe manner of the brushes N and N and are preferably placed at pointsninety degrees therefrom. They may, however, be placed in otherpositions, the essential feature being that they be at points of equaland like potential. The plates of the commutator are, as hereinafterpointed out, numbered to make it more easy to locate the brushes.Provided the brushes N and N are at the points of highest efficiencyupon the commutator, the brushes V and V will then be at points of equalpotential. If, however, the brushes N and N should be at other pointsthan the points of highest efficiency, a certain difference of potentialwill exist between the brushes V and V and a corresponding current willbe delivered through the conductors l2 and- 13, connected therewith, tothe armature u of the subsidiary motor U. This will cause the armature uto revolve, and the shaft to extended therefrom will revolve in acorresponding direction. This shaft carries a worm gearing with teethupon the wheel or ring S, and thus by the revolution of the armature ofthe motor the brushes N and N will be adjusted in the direction requiredto place them at the proper points with reference to the commutator, itbeing understood that the connections through the armature of the motorU are such as to cause it to revolve in the proper direction to placethe brushes V and V at the points of equal potential upon theco1nmutator. The supplementary brushes V and V are not placed, it shouldbe observed, in contact with the same segments of thecommutator as thebrushes Nand N but are arranged to make contact only with, for instance,every third or fourth segment. This result is secured in a convenientmanner by longitudinally extending certain of the cont-actplates, asdesired, beyond the others, as shown at w w in Fig. 5. The intermediatecontact-plates are shorter and come beneath the brushes N and N only.The spaces between the extended plates are, however, preferably filledby short plates of the same material for the purpose of causing an evenwear upon the surfaces of the commutator. The individualcommutatorplates are preferably numbered or otherwise arbitrarilydesignated. This renders it easy to determine by inspection which arediametrically opposed and which are separated by an angle of ninetydegrees.

In Fig. 9 a modification is illustrated in which a differentorganization of circuits for the motor is adapted. In this figure theconductor 1, leading from the contact-wheel H, passes through anadjustable resistance, R, of a character presently to be described,thence to the field-magnets of the motor and through a circuit-reversingdevice, K, for the armature. From the armature the connections arecontinued to the return-conductor by the car wheels. The reversingdevice consists of four contact-points, k k It It, to which twocircuitclosing points, K K", carried by an arm, 0, are applied. The arm0 is coupled to a wheel, a, geared to the shaft u of the supplementarymotor U, by means of which the commutatorbrushes V and V are regulated.By continuing the revolution of the supplementary motor thecircuit-reversing plates K and K may be carried from one pair to theother of the contact -plates, thus reversing the circuit through thearmature. The revolution of the shaft of the supplementary motor will atthe same time act through its gearing with the commutatorring S toreverse the position of the brushes of the commutator. As it isnecessary, however, that the reversals should not take place when toostrong a current is traversing the armature of the motor, it ispreferred to interrupt the connections of the armature during the timeof the reversal. this purpose the arm 0 of the reversing device extendsloosely through the support for the plates, and two adjustable nuts, 0and 0, determine the play which it shall have. By means of these nutsthe circuit-closingplates may be drawn from one pair of contact-platesat the proper moment, and sufiicient time will elapse before they areplaced in contact with the other pair to allow the commutator-brushes tobe adjusted to approximately their proper positions before the circuitof the armature is again completed.

For the purpose of more readily controlling the supplemental motor itsfield-magnet is in eluded in a shunt-circuit, as before, while thearmature is included in a circuit controlled by means of a switchdevice, Y. This consists of a lever, y, having two circuit-closingplates, y and insulated from each other andrespectively connected withthe contactbrushes V and V and provided with six contact surfaces orplates, z z e z z .2. Two of these, 2 and 2 are respectively connectedwith the brushes V and V applied to the ar- For ioo

mature. \Vhen the lever stands in the position shown in the drawings,then the circuit is completed, as before, through the armature of thesupplemental motor. When it is moved into contact with the plates a and2, it serves to drive the supplemental motor in one direction, and whenmoved into contact with the plates 2 and a it drives the supplementalmotor in the opposite direction. For this purpose the two plates a andz" are respectively connected with the conductor 4 through a resistance,R and with the conductor 1. The plates 2 and a are respectivelyconnected with the plates 2 and .2.

Instead of employing the supplementary motor for adjusting the positionof the commutator-wheel S, it may be, in some instances, desired toemploy a mechanical device of any suitable character which is liberatedby an electromagnetic device.

An adjustable resistance, It, in the line 1 is preferably so constructedthat successive portions maybe introduced inniultiple are instead of inseries. This is desired for the purpose of avoiding the necessity ofemploying resistance-conductors of sufficient size to convey the entirecurrent required for the motor. The resistances areinserted one afteranother bggneansofa cam device. (Illustrated in Fig. 1

The device which it is preferred to employ for cutting the resistances r1" W, 8rd, in .and out of circuit consists of a shaft, g, which may beturned in one direction or the other by a proper system of gearing. Thisshaft carries a non-conducting section of a cylinder, q, and aconducting'segment of a cylinder, g the surfaces of which are normallyin the same cylindrical surface. The segment g is supported upon twohinges, (l q. A series of conducting-springs,- o o 72 850., are designedto be released in succession from this segment as it is turned towardthe right hand. For this purpose the segment may be ofgradually-decreasing width, as represented, and the ends of the springsarranged in astraight line, or the springs may be laid in a spiraldirection as regards the surface of the cylinder-segment, while the edgeof the plate or segment g is straight. In the form represented thesegment widens from one end to the other by steps or ledgescorresponding to the respective springs. It is desired that theinterruptions of the circuit should be quick and sudden and not gradualwhen the several resistances r r ,-&c., are to be cut out of circuit.

-For this reason the segment (I is coupled to the shaft (1 by apivotedelbow, q q The arm g is rigidly secured to the shaft,whi1e the arm linksthe edge of the segment 1 with the arm 1*. \Vhen the shaft is revolvedtoward the right hand, the elbow Q5 tends to straighten, thus throwingthe circuit interrupting edge of the segment q" outward from the shaft,and subsequently causing it to follow the movement of the shaft towardthe right hand, thus interrupting the connections one after another byallowing the springs to fall over the edge of the segment against thenon-eondueting surface of the section g of the cylinder. When it isdesired to replace the resistances, it is evident that the segment qmustfirstbebrought down to its original position-that is to say, intothe cylindrical surface of the section q?- so that the springs may slideupon its surface. To accomplish this the elbow closes and draws the edgeof the segment q down behind the edge of the cylinder-section, thusallowing the springs to pass readily into contact with theconducting-segment (f, as required. The conducting -segment (1 isconnected, with conductor 1, while the levers or springs o 12 830., arerespectively connected through the resistance-coils r r ri, 830., withthe conductor 2, leading to the field-magnet. 'When the sev-' eralleversare in contact, the several resistances are included in multiplearc. WVhen it is desired to increase the resistance, the coils ,2 .5turning the cam-cylinder and causing the levers to drop suddenly fromthe conductingsurfaces.

In constructing the resistance it is designed that the coils be so madethat the sum of their conductivities shall equal the conductivity of themain line or the conductivity of the conductors leading through themotor, and thus they will be individually of much less conaresuccessively cut out of circuit by ductivity than would be required ifthey were I placed in circuit in series.

I claim as my invention- 1. The combination, with a ear-truck, of anelectric motor supported between the axles of said truck, a crank-armupon the shaft of said motor, a coupling-bar having a sliding connectionwith said crank-arm, and a crank-pin upon one of the wheels of saidtruck coupled with said connecting-bar.

2. The combination, substantially as here inbefore set forth, with thearmature of an electric motor, of a crank-arm at one end thereof, twowheels of a vehicle, a link 0011- meeting the same, and avertically-slidingcon' nection between said crank-arm and said link.

3. The combination, with the wheels of a vehicle and their axles, of anelectric motor mounted upon said axles, intervening springs permittingslight relative movements between the axles and the motor, linkedconnections between the wheels upon each side of the vehicle, crank-armscarried upon the shaft of the motor, and vertically-yielding connectionsbetween said crank-arms and the linked connections.

4. The combiuati'omwith the driving-wheels of a vehicle, of crank-pinsupon the same, a horizontal link connecting the crank-pins, an electricmotor mounted upon the axles of said wheels, having its axis in theplane of the axes of the drivingwheels, a crank upon the shaft of themotor, and a vertically-yielding connection between the crank and saidlink.

5. The combination, with the wheels of a vehicle, of crank-pins carriedthereby, links connecting the crank-pins of the wheels upon each side ofthe vehicle, an electric motor carried upon the axes of said wheels andhaving the axis of its armature in the plane of the axes of said wheels,a crank at each end of the armature axis, said cranks being set at anangle with reference to each other, and vertically-yielding connectionsbetween the cranks and the respective links.

6. An electric motor, in combination with a truck between the axles ofwhich it is supported, and a vehicle supported upon said motor.

7. In an'electric locomotive, the combination, with the armature and thefield-magnets, of the-axles of the locomotive, the boxes at the ends ofthe fieldmagnets, into which said axles extend, bearing-blocks for saidaxles, and yielding springs between said blocks and the upper portionsof said boxes.

8. The combination, with an electric motor, of two pairs of wheels andtheir respective axles, the body ofa car, a turn-table supported on themotor, through which said car bears upon said electric motor, and ayielding support between said body and said axles.

9. In an electric machine, an armaturecore composed of insulated platesof soft iron and interposed zinc plates, substantially as described.

10. In an electric machine, an armature consisting of a core composed ofplates of soft iron separated from each other, with plates of zincinterspersed therewith, and bobbins of insulated wire binding the platestogether, substantially as described.

11. The combination, with an electric motor, of a contact-wheeladjustable in an angular direction from the line of travel, a springtending to force the wheel downward, an adjustable stop forlimiting thedownward thrust, and a quadrant and arm applied thereto for regulatingthe angular position of the contactwheel.

12. The combination, substantially as hereinbefore set forth, with anelectric motor, of conductors for supplying currents thereto, a

lengths, certain of which segments extend across the width of thecommutator, while others are insulated at certain predetermined points.

14. The combination, with the armature of an electric motor, of acommutator having certain of the commutating-plates extended beyond theothers, a pair of brushes applied to the commutator, and a second pairof contactbrushes applied to the extended plates, substantially asdescribed.

15. An electric circuit-controller consisting of a series ofcontact-springs, a contact-surface in the form of a segment ofacylinder, a shaft upon which it is loosely mounted, a knee-jointconnecting the same with the shaft, whereby one edge may be thrown agreater or less distance from the shaft, and a non-conductingstriking-surface for the spring.

16. A circuit-controlling device consisting of a series ofcontact-springs, a contact-plate movable in one direction or theotherbeneath the springs, means for forcing the plates against thepressure of the springs when it is to be moved in a direction forreleasing the latter and for forcing it in the opposite direction whenit is to be passed beneath the springs, and a nonconductingbearing-surface for said springs when they are released from thecontactplate.

In testimony whereof I have hereunto subscribed my name this 23d day ofNovember, A. D. 1886.

STEPHEN DUDLEY FIELD.

\Vitnesses:

DANL. W. EDGEcoMB, CHARLES A. TERRY.

